The present invention relates to a continuous press of a screw press type comprising a screw shaft arranged rotatably, a screw drum arranged around said screw shaft to rotate therewith, a screw blade arranged helically around the outer surface of said screw drum, an outer drum arranged around said screw blade and having a number of small filtering holes, an inlet provided at one end of said outer drum and an outlet provided at the other end of said outer drum, whereby raw materials to be pressed are introduced through said inlet into a space between said screw drum and outer drum, said space being gradually made small in a direction from said inlet to said outlet.
Such a continuous press has been widely used for continuously pressing water, oils and fats out of raw materials such as paper pulp, bony parts and guts of fishes, etc. However the filtering efficiency of the known continuous press is limited to a certain range and such a low efficiency could not be improved except by designing the press in a suitable manner. For example, water in paper making sludge can be pressed only to such an extent that a cake at a press outlet contains water by an amount of 60-70 percentages by weight and in case of bony parts and guts of fishes a cake still contains water by an amount of about 60 percentages by weight. This is an obstacle to succeeding steps. Moreover, oils and fats contained in bony parts and guts of fishes could hardly be filtered away merely by pressing them with known presses. Further an electric motor for rotating the screw shaft and screw drum is liable to be overloaded, because raw materials stick to the surfaces of the screw drum and screw blade.
The present invention has for its object to provide a continuous press or filter in which a high filtering efficiency can be attained and a load for the electric motor for rotating the screw shaft can be materially decreased.
It is another object of the invention to provide a continuous press which can press even oils and fats contained in materials such as bony parts and guts of fishes.